How to Do the Crunch

How to Do the Crunch -- Starting Position

The 'crunch' has replaced the 'situp' for most purposes because of concerns about lower back injury and that situps may be less effective than crunches for abdominal strengthening, although this is not accepted by every authority. With the crunch, the lower back stays on the ground and you raise the shoulders while contracting the abdominals muscles.

Crunches take many forms including the standard supine floor crunch, reverse crunch, crunch with weights and on a fit ball, combined crunch and twist crunch. This description features the standard floor crunch.

Muscles worked: rectus abdominis (six-pack) with some activation of the external obliques (muscles at the sides of the abdomen).

Positioning the Body

  • Lie on the floor face up with hands behind the head. Don’t clasp the fingers behind the head. The hands should not propel the head forward in this exercise.

  • Legs are bent at approximately right angles at the knee with feet flat on the floor, shoulder width apart.

  • Brace the abdominal muscles and hold a neutral spine position with a slight natural curve in the lower back (lumbar) region yet with the back firmly against the floor.

How to Do the Crunch - Body Movement


  • Move the shoulders upward and curl slightly forward as you contract the abdominals until the shoulder blades are about two to three inches (5-7 centimetres) off the floor, or about 30 degrees; hold for about two seconds.

  • Unlike the squat and deadlift, a curl forward with the upper back and shoulders is necessary with the crunch and an arched back is contra-indicated because of biomechanical forces pulling on the spine.

  • Exhale as you come up and inhale as you return in preparation for the next repetition. Don’t hold the breath on the up movement. Contracting the abdominals does not mean holding the breath. The head should be kept straight and the chin should not drop to the chest.

  • Return to the starting position under control. Don’t flop down. Try ten repetitions for three sets starting out and increase it as you get stronger.

  • A reverse crunch has the arms by the sides and legs bent at the knees, feet off the floor with lower legs parallel to the floor. The legs are ‘reversed’ toward the chest with hips raised slightly from the floor.

  • A 'combined crunch' integrates both shoulder and leg/hip movement in one exercise. This is a very powerful advanced exercise working the rectus abdominis and the external obliques, the muscles at the sides of the abdominal area.

  • When you can do three sets of fifteen combined crunches you know your abs (and hip flexors) are in good shape.

How to Do the Crunch - Check Points

Check Points

  • Brace the abs ready for the lift.

  • Don’t lift the feet or back off the floor (in the standard crunch).

  • Do keep the head still and chin up.

  • Do lower under control and don’t flop.

  • Remember to breathe normally.

  • Don’t try to get the shoulders too high in the crunch and remember you don’t want the lower back to rise in this exercise. Think of the shoulder blades as the dividing line.

Crunch away and get those stomach muscles ready for anything. In fact, strengthening the abdominal muscles will prepare you not only for vigorous sporting activity but for those active tasks around the home, like gardening, where bending and twisting and reaching are paramount.

If you need to, check out the the top ten list and the basic training and safety information.

Congratulations bootcampers, you've nearly finished the complete full-body workout. After you do three sets of ten crunches you can head on over to the treadmill and give me three miles (4.8 kilometres) in 30 minutes including a tapered cool-down with stretches. Or you can save the cardio for another day if you've had enough. I talk more about mixing weights and cardio in my Circuit Fit program.

Don't forget to rehydrate with water or perhaps a sports drink, and refuel with some carbohydrate within about 30 minutes for best effect, particularly if you finished off with the cardio.

Watch the Exercise Gallery for additional and more advanced exercises.

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